An armed man was in a standoff with law enforcement in Ohio on Thursday after threatening the Cincinnati FBI building, leading to a chase and a shootout.

The incident began when the suspect “attempted to breach the Visitor Screening Facility” at the FBI building at approximately 9 a.m., the Cincinnati FBI office told the New York Post.

They added that the gunman then travelled north “after an alarm and a response by FBI special agents.”

According to NBC News, the suspect fired a nail gun at FBI staff at the building and also held up an AR-15 type rifle.

“At approximately 9 AM this morning an armed subject attempted to breach the Visitor Screening Facility at FBI Cincinnati. After an alarm and a response by FBI special agents, the subject fled north onto Interstate 71,” FBI Cincinnati tweeted.

In response, police closed Interstate 71 and State Route 73 in both directions, and a lockdown order was put in place for Clinton County, in the northeast part of Cincinnati, the county Emergency Management Agency (EMA) said on Facebook.

They added that the gunman had on a grey shirt and body armour.

Some time later, law enforcement became involved in a shootout wth the suspect during a standoff in a cornfield, with both sides exchanging fire.

As of 12:30 p.m. on Thursday, the EMA said the suspect was still at large but the situation had been “contained.” The area was still on lockdown.